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There are two National Priorities List (NPL) sites in Monticello, San Juan County, Utah: the Monticello Mill Tailings Site (MMTS) and the Monticello Vicinity Properties (MVP). Bothsites are associated with the Monticello Uranium Mill.

The Monticello Mill Tailings Site is a former uranium and vanadium processing mill. It isdivided into three distinct operable units: the mill site tailings and mill site property; theperipheral properties; and surface water, groundwater, and contaminated sediments in Montezuma Creek Canyon. The mill posed a public health hazard when it was operating. Thetailings that remain on the mill site would be a public health hazard today if the public hadaccess to the mill site. However, access is strictly controlled: the mill site, therefore, does notpose a threat to area residents.

The Monticello Vicinity Properties are off-site residential and commercial properties. Land useof most of these properties is residential housing. The community will continue to be exposed tolow-level radiation until remediation is complete. The remedial actions will eventually removemost of the contaminated soils within the residential community, thereby eliminating concernsabout long-term exposure.

For the purpose of this public health assessment, on site describes the actual mill site itself andoff site describes all other areas (vicinity and peripheral properties).

There are several sources of contamination in soils and buildings throughout the city ofMonticello: the mill tailings which, in the past, were windblown into the city, were prevalentthroughout the southeastern quadrant, and were also taken from the mill site and used as fill foropen lands; backfill around water, sewer, and electrical lines; and sand mix in concrete, plaster,and mortar. As a result, residents have been exposed to low levels of radium-226 and radon-222. Department of Energy (DOE) representatives have surveyed and recommended for clean-up inclusion a total of 449 vicinity and peripheral properties (420 vicinity and 29 peripheral). Three hundred eighty-nine vicinity properties and 11 peripheral properties have been remediated.

Agency for Toxic Substances and Disease Registry (ATSDR) staff members believe thatexposures were greater in the past than they are today. Industrial hygiene surveys of the millperformed when the mill was operating reported that conditions were very dusty and that manyworkers were exposed to levels of radioactive dusts above allowable concentrations. Analysis ofthe available health outcome data show that San Juan County has the highest rate of renal failureamong women in the state, and limited evidence suggests that there is an increased risk of dyingof lung cancer in Monticello compared with the risk for the rest of the county. There is no supporting information connecting these incidences to the mill site.

The largest risk to the general public stems from exposure to direct gamma radiation fromunremediated soils in Montezuma Creek Canyon. However, this risk is relatively low and directgamma radiation exposure exists mostly at or near natural background levels. Thecontamination of Montezuma Creek by surface runoff of tailings from the mill site creates apotential exposure pathway. The most likely exposure would occur if hunters consumed gameanimals that had entered the mill site or the Montezuma Creek floodplain and eaten vegetation ordrunk water from either one of the areas. However, such exposures, if any, would have beenintermittent and highly unlikely to have resulted in adverse health effects. In the fall of 1996 theEnvironmental Protection Agency (EPA) and Utah Department of Environmental Quality(UDEQ) staff conducted a study of the body burden of contaminants in tissues and organs ofdeer and cattle that consumed water and vegetation from the Montezuma Creek floodplain. Cattle and deer from a background reference area were also sampled. The meat, liver kidney,and ribs are being analyzed for radionuclides and nonradionuclide contaminants. Although theanalyses have not yet been completed, preliminary results indicate little or no contaminantuptake in cattle or deer above the uptake in the reference area animals. Since 1993, drainagecontrols on-site have nearly eliminated surface water run-off contamination. Surface water run-on has been eliminated by a series of ditches that divert water around the mill site. Surfacewater on-site is collected and routed to a pond for treatment before release. The majorcontribution to surface water contamination is leachate in groundwater that enters MontezumaCreek downgradient from the mill site. Also, the shallow alluvial aquifer is contaminated withuranium-234 and uranium-238 at levels of public health concern, but there are no known privatewells associated with the aquifer and currently in use. ATSDR representatives recommend thatlocal ordinances be established to prevent future installation of wells into the contaminatedalluvial aquifer.

Monticello is in the geographic center of San Juan County. San Juan County covers a very largeand sparsely populated area of southeastern Utah. With a total area of more than 7,800 squaremiles, the county is slightly larger than New Jersey, but its 1990 population was only 12,621. At2.74 square miles, Monticello is the largest town in the county in terms of its area. More thanhalf the population of San Juan County is Native American. Monticello's 1990 population wasslightly more than 1,800.

The off-site area, the vicinity and peripheral properties, is being considered for follow-up publichealth actions. Exposure to contaminants from past and current activities at the MMTS suggeststhe need for health studies and further education efforts. ATSDR staff will conduct a needsassessment as a basis for determining the appropriate preventative health education plan for thesites. We will identify the public health problems, community concerns, health professional andcommunity-specific needs, and primary target populations for health education. Special needsgroups, such as children, minorities, and the elderly, will be noted. ATSDR staff plan tocollaborate with state and local health departments.


A. Site Description and History

The Monticello Mill Tailings Site is a 110-acre abandoned uranium and vanadium processingmill in the city of Monticello, San Juan County, in southeastern Utah. The Monticello VicinityProperties are off site residential and commercial properties. Both of the sites are associatedwith the Monticello Uranium Mill. The United States Department of Energy (DOE) owns themill site (see Appendix F, Figure 1). The City of Monticello, private residents, and the state of Utah Highway 191 right-of-way own the land that borders the mill site. No residences arewithin the mill site boundary, but residences are adjacent to the north and east edges of the millsite (1).

Operating History

The Vanadium Corporation of America opened a vanadium ore-buying station at Monticello inlate 1940 and began mill construction in 1941. In 1943, Vanadium Corporation beganproducing a uranium-vanadium sludge for the Manhattan Engineer District (1).

Construction of the Monticello plant, in addition to the mill proper, included the development ofan adequate water supply, installation of a power plant, and construction of two large housingprojects for workers. The staff town site, on the hill opposite the mill, consisted of a staff housefor 12 men, a manager's house, and 14 4-room family dwellings. The other housing projectconsisted of 32 2-room family houses and a bunkhouse and boardinghouse for 32 men (2).

Intermediate owners and operators of the Monticello Mill Tailings Site included the War AssetsOffice; the Atomic Energy Commission (AEC); American Smelting and Refining Company;Galigher Company; Lucius Pitkin, Inc.; National Lead Company; the Bureau of LandManagement (BLM) (acquired the mill site by means of a land transfer, never operated the mill);and the DOE. Mill operations were terminated on January 1, 1960. The ore-buying station remained open until March 1962 . Remediation work on the site is still being done today (1).

Milling processes used at Monticello during the 11 years of AEC operation included raw orecarbonate leach, low-temperature roast/hot carbonate leach and salt roast/hot carbonate leachuntil 1955, acid leach resin-in-pulp and raw ore carbonate leach from 1955 to 1958, and a carbonate pressure leach resin-in-pulp process from 1958 until mill closure in 1960 (1).

The mill tailings were stabilized between 1961 and 1962, and the plant was dismantled in 1964. Removal of contaminated soils from the ore-buying stations occurred between May 1974 and August 1975 (1, 3).

Remediation Activities

In 1978, the United States Department of Energy (DOE), under the authority of the AtomicEnergy Act, initiated the Surplus Facilities Management Program to assure safe caretaking anddecommissioning of government facilities that had been retired from service but still hadradioactive contamination. The Monticello Mill Tailings Site was accepted into the SurplusFacilities Management Program in 1980. The Monticello Remedial Action Project was thenestablished to restore the government-owned mill site to safe levels of radioactivity, to disposeof or contain the tailings in an environmentally safe manner, and to perform remedial actions onoff-site vicinity properties that had been contaminated by radioactive material from the mill operations.

In 1983, remedial activities for vicinity properties were separated from the Monticello RemedialAction Project with the establishment of the Monticello Vicinity Properties Project. The GrandJunction (Colorado) Projects Office of the Department of Energy conducts both the MonticelloRemedial Action Project and the Monticello Vicinity Properties Project (1).

There are two National Priorities List (NPL) sites in Monticello, the Monticello Mill TailingsSite (MMTS) and the Monticello Vicinity Properties (MVP). Both sites are associated with theMonticello Uranium Mill. The Environmental Protection Agency (EPA) formally included theMVP and the MMTS on the NPL on June 10, 1986, (4) and November 16, 1989, respectively(3). The sites are being remediated in accordance with the Monticello Vicinity PropertiesProject November 1989 Record of Decision and the Monticello Mill Tailings Site August 1990 Record of Decision.

Mill tailings and associated contaminated material remain on the mill site as a result of millingore to recover uranium and vanadium. Tailings particulate material has been blown by the windand carried by surface water to off-site properties, over time. The tailings piles have beencovered and vegetated to prevent further windblown dispersion of contaminants.

The MMTS is divided into three distinct operable units:

Operable Unit I
Operable Unit II
Operable Unit III
Mill Site Tailings and Mill Site Property
Peripheral Properties
Surface Water, Groundwater, and Contaminated Sediments in
Montezuma Creek Canyon (4, 5)

The remedial actions planned for these operable units are interdependent.

The August 1990 Monticello Mill Tailings Site Record of Decision addresses the remedialactions for Operable Units I and II. A record of decision will be prepared for Operable Unit IIIafter remedial actions for Operable Units I and II are initiated and additional monitoring data forgroundwater and surface water are collected.

The mill site consists of the former locations of the mill and residential areas, covering 32 acres,the tailings-impoundment area, covering 68 acres, and the former BLM property, covering 10acres. The land that the BLM occupied was originally part of the mill site, but that land wasdeeded back to DOE in 1992. An estimated 100,000 cubic yards of contaminated material hasbeen identified in the mill area, and approximately 1.4 million cubic yards (2 million tons) oftailings, contaminated soil, by-product material, and contaminated building material is located inthe tailings-impoundment area (4). Appendix F, Figure 2, depicts the mill site property,associated buildings, and tailings piles.

The tailings are stored in four piles:

    1. Carbonate Tailings Pile (oldest of the tailings piles),
    2. Vanadium Tailings Pile,
    3. Acid Tailings Pile (received tailings from 1955 to 1956), and
    4. East Tailings Pile (received tailings from 1956 to 1960) (1).

The peripheral properties are adjacent to the DOE property but are owned by other individualsor entities. During the period of mill operation, mill operators leased private land north andsouth of the existing mill site to stockpile ore. The former ore-stockpile areas and other adjacentareas contaminated by windblown and water-borne tailings cover approximately 300 acresaround the mill site and contain most of the estimated 300,000 cubic yards of peripheral propertymaterial to be remediated. Peripheral properties also include the bed and banks of a 3.3-milereach of Montezuma Creek between the city of Monticello and Vega Creek (4).

The Monticello Vicinity Properties (MVP), also referred to as the Monticello RadioactivelyContaminated Properties, are off-site residential and commercial properties. Land use of most ofthese properties is residential housing. Adjacent land usage includes heavy and light commercialuse and a "controlled" zoning district that allows a mix of agricultural, residential, industrial, andcommercial use (3).

Throughout the operating period of the Monticello Uranium Mill, mill tailings from the mill sitewere windblown into the city of Monticello or used in construction in the city of Monticello. Windblown tailings contamination is prevalent throughout the southeastern quadrant of the city. The tailings were used as fill for open lands; backfill around water, sewer, and electrical lines;sub-base for driveways, sidewalks, and concrete slabs; backfill against basement foundations;and sand mix in concrete, plaster, and mortar. The total tonnage of uranium mill tailingsremoved from the mill site for construction purposes was never documented. However,contaminated material from the vicinity properties is estimated at 156,000 cubic yards. Theremoval of contaminated tailings from the mill site was restricted in August 1975, when a fencewas erected around the mill site to prevent unauthorized access and the ore-buying stations werecleaned up. Appendix F, Figure 3, outlines the MVP project area and shows the adjacent mill site location (3).

Remediation began in 1984, and Appendix F, Figure 4, depicts the status of the MonticelloVicinity Properties as of February 1995.

According to the EPA Region VIII Hazardous Waste Management Division Five-Year Review(Type Ia) document, 420 individual properties were included in the Monticello VicinityProperties (MVP) Site as of December 1996. This document covers the first 5-year reviewperiod from 1991 through 1996. DOE is the responsible party for remediating the MVP and isfurther responsible for certifying that the remediation is completed at each of the properties. These 420 individual properties are grouped into eight operable units, designated A through H. These operable units are defined for administrative convenience and, except for Operable UnitE, do not imply geographic proximity of individual properties to each other. For fiscal year1996, 14 remedial actions were completed and by the end of 1996, 389 properties wereremediated on the MVP Site. There are an additional 29 peripheral properties. As of May 1997,11 peripheral properties were remediated (5, 6).

The MVP is divided into 8 distinct operable units (OU):

    Operable Unit A. OU A consists of 104 properties. As of May 15, 1996, remedialconstruction for this OU was complete. A draft-final Remedial Action Report wassubmitted November 8, 1996. The report was approved by EPA, with the concurrence of the state, on January 13, 1997.

    Operable Unit B. OU B consists of 243 properties. As of December 13, 1996,construction was complete at 237 properties; 3 properties were under construction; and 3properties did not require remedial action.

    Operable Unit C. OU C consists of 34 properties. Contamination is traceable to uraniummilling at Dry Valley, Utah, or to other sources not associated with the MonticelloUranium Mill. As of December 13, 1996, construction was complete at 32 properties; 1 property was scheduled to be remediated; and 1 property did not require remedial action.

    Operable Unit D. OU D consists of six properties. These are properties on whichnonradiological hazardous substances are known or suspected to exist. As of December13, 1996, construction was complete on three properties and three properties were under construction.

    Operable Unit E. OU E consists of eight properties. These properties are crossed byHalls' Ditch, an irrigation ditch that passes through the mill site. As of December 13,1996, remedial action was in progress on these properties.

    Operable Unit F. OU F consists of ten properties. As of December 13, 1996,construction was completed on 4 properties. Owner negotiations are complete on 3 of the properties. The remaining 3 properties are still in negotiation.

    Operable Unit G. OU G consists of ten properties. As of December 13, 1996,construction was completed on 3 properties. Remediation will not be required on oneproperty because contamination does not exceed standards. The remaining 6 propertiesare either in design or scheduled for construction.

    Operable Unit H. There are five properties being considered for supplemental standardswithin the MVP site. One of the properties is privately owned and the owner hasrequested DOE not to proceed with the remedial action due to the environmentaldegradation that will result from the cleanup work. Four of the properties are associatedwith the Highway 191 embankment where the cost of remediation may be excessivecompared to the reduction in risk achieved by remediation. Supplemental standards arealso being considered for city streets and utilities within the MVP site boundary. OnDecember 23, 1996, EPA and Utah Department of Environmental (UDEQ) concurred,with comment, on the use of supplemental standards at the proposed properties. Negotiations on specific issues are under way (5, 6, 7).

In January 1996, DOE proposed to the regulators to remediate soils in the upper part ofMontezuma Creek Canyon, and to perform risk assessments to determine the need forremediation in the middle and lower parts of the canyon. These actions will remove the primarysource of risk to human health in the canyon. DOE, EPA, and UDEQ decided to defer the decision for remedial action of the upper canyon until the risk assessments are finalized.

All surface contaminants posing an unacceptable risk to human health and the environment willbe placed in the permanent repository immediately south of Monticello. In late May, 1997,DOE began placement of approximately 2.3 million cubic yards of mill tailings and othercontaminated materials in the recently completed repository. Excavation has begun on theCarbonate Tailings Pile on the north side of the former mill site. The excavation andtransportation of the tailings should be in full swing by June 20, 1997. The excavation andhauling will be conducted 7 days per week, 12 hours per day. The excavation activities will becompleted by November 1998.

The Agency for Toxic Substances and Disease Registry (ATSDR) released the Monticello MillTailings and Monticello Radioactively Contaminated Properties (aka Monticello VicinityProperties) Public Health Assessment for public comment on December 20, 1996. The officialcomment period ended on February 21, 1997. Several new DOE documents have been releasedand become available during the finalization of this public health assessment. ATSDR scientistsrequested, received, and reviewed these documents. These documents did contain in-depthvaluable information. ATSDR updated the conclusions and recommendations of this documentto reflect this more recent information.

Following is a synopsis of the newly released documents:

Operable Unit III Baseline Human Health Risk Assessment, March 1997--This documentillustrates that when the risk is characterized in terms of the potential numbers of personsexposed, added cancer mortality associated with exposure to Operable Unit III contaminants isunlikely and would be indistinguishable from the background cancer mortality rate (8).

Operable Unit III Alternatives Analysis, Draft, May 1997--The purpose of this alternativesanalysis is to identify and evaluate remediation alternatives for soil and sediment in the vicinityof Montezuma Creek, which is part of Operable Unit III of the Monticello Mill Tailings Site. This report is being prepared to support a non-time-critical removal action. A removal action isbeing pursued so an expedited remediation decision can be made for soil and sediment. Recommended removal actions for each reach of Montezuma Creek (Upper, Middle, and Lower)will be included in the future draft final and final versions of the document. The state willreview the draft Alternatives Analysis Report and provide input on the alternatives. Input fromthe state will be incorporated under "State Acceptance" in the Draft Final Alternatives AnalysisReport. DOE staff will then hold a landowner briefing to get input on the alternatives from theproperty owners. After input from the state and the landowners is incorporated into theAlternatives Analysis Report, the risk managers (i.e., DOE, EPA, and the state of Utah) willselect recommended removal actions for soil and sediment in Upper, Middle, and LowerMontezuma Creek and present the information at a public meeting (9).

Operable Unit III Ecological Risk Assessment, Draft, June 1997--Only the aquatic communitymay be of "possible concern," although actual risks may be of "no concern." There is littlelikelihood that the Operable Unit III contaminants of concern are harming the other receptors. This conclusion is substantiated by the tissue sampling done for the cliff swallows (surrogate forthe southwestern will flycatcher) and mule deer, which indicated that concentrations ofcontaminants of concern concentration in these tissues are not elevated. These findings need tobe contrasted to short-term and long-term impacts to these receptors and their ecosystems thatwould occur during remediation. The potential impacts from remediation will be discussed inthe alternative analysis for Operable Unit III soil and sediment (10).

ATSDR scientists will continue to review any future documents that become available. Shouldadditional information become available that alters the findings of this public health assessmentor addresses issues described herein, this public health assessment will be modified as needed.

ATSDR Activities

The Agency for Toxic Substances and Disease Registry (ATSDR) released a preliminary publichealth assessment for the Monticello Radioactively Contaminated Properties National PrioritiesList Site, more commonly referred to as the Monticello Vicinity Properties (MVP), in July 1988. The preliminary public health assessment concluded that the MVP site was of public healthconcern because of the risk to human health from exposure to hazardous substances. Assessorsdetermined that people could be exposed during domestic uses of contaminated groundwater andby eating garden vegetables grown in contaminated soil. The document recommended thatfuture environmental investigations be designed to address environmental and human exposure pathways.

ATSDR also released a site review and update (SRU) for the MVP in September 1992. TheSRU concluded that although the community will continue to be exposed to low-level radiationuntil remediation is complete, the remedial actions will eventually remove most of thecontaminated soils within the residential community, thereby eliminating concerns about long-term exposure from outside sources. However, there are properties in the community that maynot be addressed by the current remedial actions for various reasons (i.e., properties whoseowners have refused remediation, areas outside the 8-mile radius clean-up boundary, propertiesthat contain naturally occurring radioactive materials (NORM), or properties where the brickveneer was left behind and, as a result, small sections of the community may continue to beexposed to low levels of radiation. The original clean-up boundary (6-mile radius) of the MVPswere those properties within the city limits. Peripheral properties generally lie outside theMonticello city limits. The new clean-up boundary extends to an 8-mile radius. DOErepresentatives, at the insistence of EPA and UDEQ, sent letters to all property owners withinthe 8-mile radius of the mill site. If owners suspected that tailings or materials from the mill sitewere on their property, they were requested to notify DOE. If contacted, DOE staff conductedradiological surveys of the property. Five additional properties have been included as a result ofthe surveys. Unless supplemental standards are approved, properties will be cleaned up to the 40Code of Federal Regulation (CFR) 192.12 standard. EPA and UDEQ will considersupplemental standards (alternative clean-up levels including institutional controls) only if theyare protective of human health and the environment. In November 1996, DOE released a draftfinal General Radiological Risk Assessment Methods document. The methods described in thisdocument are intended for assessing exposure, dose, and risk for candidate supplementalstandards properties. A risk assessment will be developed for each property using site-specificdata, and these methods will be used to derive supplemental standards for evaluating responsealternatives. If remedial actions are considered as a response alternative, the supplementalstandards will serve as target performance goals. These methods provide supplemental standardsthat ensure overall protection of human health and the environment and compliance withapplicable or relevant and appropriate requirements (11). EPA and UDEQ have no statutoryrequirement to clean up NORM. Property owners with such materials will be contacted andgiven the opportunity to have NORM disposed of in a repository.

The 1988 preliminary public health assessment discussed possible contamination of off-sitegroundwater and possible contamination of vegetables from home gardens as a concern at theMVP. The SRU concluded that groundwater contamination does not appear to be a problem atthe MVP site, but does appear to be a concern at the MMTS. The Operable Unit IIIinvestigation addresses groundwater and surface water issues at the MMTS, and remediation ofthe soil should eliminate the possibility of contaminated vegetables. Currently, produce are notbeing grown within Operable Unit III or in the Montezuma Creek Canyon. The documentrecommended a health consultation to evaluate data on the disputed properties (disputedproperties are no longer an issue, DOE representatives have agreed to remediate all propertiesinside the cleanup boundary), removal of tailings from the Monticello area, and naturallyoccurring radioactive materials such as rock collections. The document also recommended thatworkers for the City of Monticello use radiation detectors while conducting municipalimprovements that require excavation of soils in areas where the soils have not been characterized for radioactivity (12).

B. Site Visits

ATSDR headquarters staff members and the ATSDR Region VIII representative conducted thefirst MMTS and MVP site visit July 20-24, 1992. They met with representatives of DOE;Chem-Nuclear Geotech; EPA Region VIII; other federal, state, and local environmental andhealth officials; and Monticello city officials. DOE and Chem-Nuclear Geotech staff membersprovided an overview and tour of the MMTS and the MVP.

Site visitors observed that small gardens are common in the community. Also, soils on andaround the MMTS generally appeared to have some form of vegetation. The MVP locationswere under remediation. The remediation debris from these off-site properties was beingtrucked to and then temporarily stored on top of the East Tailings Pile. Remediation workerswere practicing dust-control measures to minimize redistribution of the contaminated material. City workers were improving the water system, and piles of soil marked areas whereimprovements were being installed throughout the community.

Staff members from the EPA's National Air and Radiation Environmental Laboratory (NAREL)and from Boston University (BU) accompanied ATSDR representatives on a second site visit,which took place from October 4 to 8, 1993. NAREL staff members helped ATSDR withradiation evaluation, and BU staff members helped to evaluate community health concerns andhealth outcome data. They met with representatives of DOE, RUST Geotech (formerly Chem-Nuclear Geotech), EPA Region VIII, and the UDEQ. ATSDR staff members also met withMonticello community members and city officials to gather community health concerns. ATSDR representatives performed an introductory orientation at two DOE-hosted publicmeetings. There were no significant observations other than those already mentioned in thebackground and history portions of this document.

ATSDR representatives conducted public availability sessions in Monticello and Blanding fromDecember 7 to 8, 1993. ATSDR staff members met informally with individuals or small groupsof community members during the trip and the public availability sessions, which helped togather health information and collect community concerns. They interviewed approximately160 community residents and concerned residents. A variety of questions and concerns werecollected. Community members indicated that a group of concerned residents existed in thenorthwest quadrant of Monticello. These residents filed a lawsuit against the National LeadCompany, the contractor that operated the Monticello Uranium Mill before the mill closed in 1960, for the multiple deaths of children from leukemia (13).

ATSDR and NAREL staff members provided information on radiation and health issues duringcommunity information sharing sessions from April 24 to 27, 1995. They discussed whatradioactive materials, radiation, and contamination are; how we locate radioactive materials andmeasure radiation; how we are exposed to radiation in our environment and from naturallyoccurring radioactive materials inside the human body; the possible health effects of exposure toradiation; and how we protect ourselves from radiation sources. They conducted 13 communityradiation and health information-sharing sessions in Monticello and Blanding. The audienceincluded community members, groups of students, Blue Mountain Dineh (Navajo), and WhiteMesa Utes. Attendance at each session was as follows:

Sessions 1 & 2
Session 3
Session 4
Session 5
Session 6
Session 7
Session 8
Sessions 9 & 10
Session 11
Session 12
Session 13
Blanding Elementary School = 650 students
San Juan High School = 35 students
Blanding Middle School = 10 students
Blanding Community = 4 people
Monticello High School = 40 students
Monticello Community (Session A) = 4 people
Monticello Community (Session B) = 6 people
Monticello Elementary School = 325 students
San Juan High School = 12 students
Blue Mountain Dineh = 10 people
White Mesa Utes = 2 people.

C. Demographics, Land Use, and Natural Resource Use

Appendix A, Tables A1-A3, and Appendix F, Figures 5-9, present demographic information.

C.1 Demographics

Monticello is in the geographic center of San Juan County, Utah. The city of Monticello wasestablished in 1888 and was named for Thomas Jefferson's home in Virginia because of similarities in geography.

Data used in Appendix A, Tables A1-A3 and the following text are approximations from the1990 Census of Population and Housing for San Juan County and Monticello (14). Figures 5-9in Appendix F present demographic data extracted from the United States Bureau of the CensusTopologically Integrated Geographic Encoding and Referencing (TIGER) system (15). TheTIGER system was launched in 1983 to automate the mapping and other geographic activitiesrequired to support the bureau's censuses and surveys.

San Juan County covers a very large and sparsely populated area of southeastern Utah. With atotal area of more than 7,800 square miles, the county is slightly larger than New Jersey, but its1990 population was only 12,621. More than half the population of San Juan County is NativeAmerican. At 2.74 square miles, Monticello is the largest town in the county in terms of its area. Monticello's 1990 population was slightly more than 1,800. In contrast to the population of thecounty as a whole, more than 87% of Monticello's residents are white; 12.3% are of Hispanicorigin. Persons of Hispanic origin may be of any race. Extraordinarily high percentages of thepopulation for both the city, 41.4%, and the county, 43.3%, are under age 18.

There were 3.26 persons per household in Monticello in 1990, which is well above the nationalaverage of about 2.6 but is consistent with the town's large percentage of persons under age 18. (A household is an occupied housing unit, but the definition does not include such groupquarters as military barracks, prisons, and college dormitories.) Nearly 80% of Monticello'shouseholds are owner-occupied, which suggests a stable, nontransient population. Homeownerstend not to move as often as do renters. The cost of housing in isolated rural areas is typicallymuch lower than in metropolitan areas. What appears to be relatively low mean value of owner-occupied housing ($55,300) and rent paid for renter-occupied housing ($199 per month) in Monticello is consistent with that fact.

The median household income is $25,787, and the per capita income is $8,615 for Monticello. San Juan is one of the nation's poorest counties, with 36.4% of the population below the povertylevel. Monticello has a poverty rate of 12.6%. More than three-fourths of Monticello residentsaged 25 and older have a high school equivalency or higher educational background, whichindicates a relatively well-educated community.

C.2 Land Use

San Juan County, the largest county in Utah, comprises 5,045,760 acres, most of which issparsely populated rangeland and forest. Most county land is managed by either the federalgovernment or the Navajo Indian Nation. The U.S. Forest Service (Manti-La Sal NationalForest), the Bureau of Land Management (San Juan District Office), and the National ParkService manage approximately 61% of the land in the county, and the Navajo Indian Reservationencompasses another 25% along the county's southern border. The state of Utah administers6%, and less than 1% of that 6% is owned by cities and the county. The remaining 8% is privately owned land, located primarily in Monticello and Blanding (1).

Historically, the primary uses of county lands have been mining, farming/ranching, andrecreation (e.g., camping, hiking, and hunting). Mining in Utah, as in other western states, issubject to supply and demand, and thus has been cyclical. Oil, gas, and uranium are the primarymineral resources of interest in the county. Utah is the fourth largest U.S. producer of oil andgas, although no major oil or gas fields are located in the immediate vicinity of Monticello (1).

Uranium ores have been found locally in approximately half of the county, including areas closeto Monticello. However, the uranium market has been depressed since 1982, and White MesaMill is the only active uranium processing facility in the county (1). Since 1995, White MesaMill has been the only active mill in the United States.

Farming and ranching, the latter primarily cattle and sheep grazing, are common throughout thecounty. A total of 213 farms and ranches use approximately 8% of county land (411,693 acres)for agricultural purposes (1).

Most recreational use occurs in the many parks, forests, and proposed wilderness areas, anumber of which are relatively close to Monticello. The largest of the parks is CanyonlandsNational Park. The South Unit entrance of Canyonlands is 15 miles north of Monticello. LakePowell is approximately 100 miles southwest, with approximately 1,000 miles of its coastline inSan Juan County (1).

Five zoning districts have been established within San Juan County: multiple-use, agricultural,rural residential, controlled, and Indian reservation. Within the city limits of Monticello, areashave been zoned for heavy and light commercial use and for residential use. Commercial zoningalong the major thoroughfares of Monticello, U.S. Highway 191 and U.S. Highway 666, hasestablished a central business district. Commercial growth has occurred to the north and east,radiating from the center of town along those routes. Heavy commercial (formerly industrial)zoning exists in the southeastern corner of the city. The mill site and tailings piles lie south ofthis area, within a controlled district that permits a mix of agricultural, residential, industrial, andcommercial use. Several residences have been built east and immediately north of the mill site,but otherwise most of the land is nonresidential. Alfalfa for livestock feeding is grownimmediately east of the mill site. Land to the south is marginal for grazing (11).

C.3 Natural Resource Use

    a. Surface Water

    All domestic surface water resources for the Monticello area are upgradient from the millsite. The City of Monticello public water system draws from two sources: the springslocated on the flanks of the Abajo Mountains and the Monticello Reservoir on SouthCreek 1 mile southwest of the mill site. The raw water from those sources is treated,stored, and used as the public drinking-water supply, with the current treatment capacityof the public water system at 1.2 million gallons per day. The municipal distributionsystem has 650 residential and commercial connections, serving 2,000 people (16).

    Blue Mountain Irrigation District has a permit to irrigate approximately 1,000 acres withsurface water diverted from South Creek. A ditch originating at South Creek upgradientof the mill site diverts water to irrigation sites east of Monticello. The irrigation seasonbegins April 1 and ends around mid-July, when surface water ceases to flow in SouthCreek. Montezuma Creek runs through the mill site, and return flow of irrigation waterto Montezuma Creek occurs downstream from the tailings area. Additional water rightspermit downstream landowners to draw agricultural irrigation water from MontezumaCreek. The creek provides drinking water for livestock (1).

    b. Groundwater

    The source of potable water (water used for drinking, cooking, showering, etc.) for thosepeople living outside the city of Monticello is predominantly groundwater. Privategroundwater wells penetrate the Dakota Sandstone Aquitard (a geological formation thatimpedes groundwater flow from one aquifer to another) and draw water from the lowerBurro Canyon Aquifer. The shallow (upper) alluvial aquifer is currently not used as a potable water source (16).

    Groundwater is also used for irrigation in the Montezuma Creek area, whichencompasses the entire Montezuma Creek drainage area as far as the creek's confluencewith the San Juan River. Existing water rights permit irrigation of some 299 acres withgroundwater as the sole supply and another 1,718 acres with groundwater as asupplemental supply. Groundwater is not currently being used for irrigation in the areaimmediately downgradient from the mill site (1).

D. Health Outcome Data Sources

Health outcome data for Utah and the vicinity of the Monticello Mill Tailings Site and theMonticello Vicinity Properties are available from a variety of sources. The sources reviewed forthis public health assessment are described below.

  1. The Utah Cancer Registry was started in 1966 and is supported by the National Cancer Institute and contracted with the Utah Department of Health. Utah cancer mortality rates were calculated from death certificates provided by the Utah Bureau of Vital Statistics. The publication Cancer in Utah 1966-1990, compiled by the Utah Cancer Registry, was reviewed.
  2. The National Cancer Institute and the EPA have produced the Riggan's Mortality Tapes, a database that provides a comparison of the number of deaths resulting from a specific cancer type in a specified county (San Juan) and state (Utah) with the numbers of deaths from the same type of cancer for the entire United States over a period of 30 years in 10-year increments.
  3. The Utah Department of Health Bureau of Vital Records and Health Statistics provided a diskette containing information on all Utah deaths from 1956 to 1992. These data were coded to reflect cause of death, age at death, year of death, residence (both town and county), and other case-specific information. These data allowed us to analyze causes of death in Monticello and Blanding during different periods and compare them with the rates for rest of San Juan County and for Utah as a whole.
  4. A residents' survey of health problems in residents of Monticello from the 1940s through the 1960s was conducted during the last few years. Survey information was available on approximately 250 such individuals, some of whom had moved away from Monticello since the early 1970s and some of whom are still residents. Information from the survey was put on a computer database, without personal identifiers, and provided to Boston University staff members for analysis. Although this survey was conducted by volunteers and is not a complete sample of all the residents of the town during the years of interest, it nevertheless has value in identifying issues that might be addressed in future studies.
  5. Cancer Cases for Monticello, prepared by the Utah Cancer Registry, lists the number of adult and childhood cancer cases in Monticello by primary site and year of diagnosis, 1967 to 1992. The report does not list the cases by sex.
  6. WONDER: Wide-Ranging ONline Data for Epidemiologic Research is a computer database designed by the Information Resources Management Office, Centers for Disease Control and Prevention (CDC). The mortality section of the database provided information for comparing the rates of the county with rates for the state and the rest of the country.
  7. The state of Utah does not have a birth defects registry. However, a summary report, Congenital Malformations in Utah, by Seegmiller and Hansen, in Teratology Volume 22, 1980 for the years 1968 to 1972 was available.
  8. Interim Report of a Health Study of the Uranium Mines and Mills by the Federal Security Agency Public Health Service, Division of Occupational Health, and the Colorado State Department of Public Health, May 1952, contains information about uranium millers.
  9. "Cancer Mortality Patterns Among U.S. Uranium Miners and Millers, 1950 through 1962," Journal of the National Cancer Institute, is a journal article containing information about cancer mortality patterns among uranium miners and millers for the cohort study that lasted 12 years.
  10. "Cancer Mortality Among Uranium Mill Workers," Journal of Occupational Medicine, January 1973, is a continuing study and follow-up to the previous journal article (number 9).
  11. ATSDR scientists reviewed "Health Concerns in Uranium Mining and Milling," Journal of Occupational Medicine, July 1981, which is a compilation of health concerns gathered from uranium miners and millers.
  12. Mortality Patterns Among a Retrospective Cohort of Uranium Mill Workers, NationalInstitute for Occupational Safety and Health, Division of Surveillance, HazardEvaluations and Field Studies, November 1983, is an article containing an analysis of themortality patterns of uranium mill workers for the retrospective cohort study performedbetween 1940 and 1977.


We consolidated concerns collected from site visits, public meetings, public availability sessions,letters and phone calls to ATSDR, and site-related documents. When several people expressedthe same or similar concerns, we consolidated those concerns but took care to maintain theintegrity of the original concerns as expressed. Numbers in parentheses represent the number oftimes a given concern was reported.

Boston University staff members assembled a list of 66 individuals and organizations familiarwith the Monticello sites; we contacted most of them during site visits or follow-up telephonecalls. In addition, Boston University staff representatives reviewed 94 documents, scientificarticles, or print media articles related to community concerns at the Monticello sites. Wecategorized concerns as follows:

  1. Concerns about past site-related exposures
  2. Concerns about continuing site-related exposures
  3. General health outcome concerns
  4. Specific health outcome concerns

A. Past Site-Related Exposures

  1. People who visited the mill site (23):
    Residents reported having played on the mill site as children and that their own childrenplayed at the mill site. Some said they helped unload the trucks and shoveled off the ore. Others reported having climbed on the ore and tailings piles, swum in the tailings pond,waded in the creek on the mill site, ridden dirt bikes on the mill site, ridden sleighs on themill site, taken rocks home from the mill site, and engaged in Boy Scout trainingactivities on the mill site. Some of the children who played on the mill site got sick. Some died. Were they exposed to radiation? Were their childhood illnesses caused byexposure to radiation and other toxic substances? Could the childhood exposures causeillnesses later as adults?
  2. Mill workers exposed to hazardous materials (13):
    Workers at the mill were exposed to hazardous substances, including yellow cake(uranium oxides), black cake (vanadium oxides), uranium, vanadium, and chlorine gas. The ventilation was very poor and there was a lot of dust. Workers ate lunch on thetailings piles. Mill workers did not use safety masks and were not informed of thehazards during the time of operating the mill. Urine samples were taken, but workerswere not given the results. What are the dangers? What is going to happen to theseworkers?
  3. Releases from the mill to the environment (13):
    1. When the plant was operating, yellow dust was everywhere. Chrome was eatenoff cars. Clothes on the clotheslines would turn yellow and fall apart. Screendoors would disintegrate. The air smelled like sulfur. What was the yellow dust? What was the smell? What are the health effects?
    2. Yellow cake powder settled on the hay that our dairy cows ate. We drank themilk. The cows died.
    3. Up to 2 tons a day of ammonium nitrate was used in the precipitation process toextract uranium. The solution then went in the waste stream to the tailings piles. What are the possible harmful effects?
    4. Wind blew the dust out of uncovered ore trucks on Main Street going from themines to the mill. How would this affect people who lived there?
    5. Mill tailings got into the creek. We used the water for irrigation and our crops and animals died.
    6. When the plant was in operation, all the vegetation died on our land which wasnear the mill site. Why?
  4. Contamination from the work site going home with workers (6):
    Workers wore contaminated work clothes home (there was yellow dust on their clothesand shoes), and the clothes were washed with the family wash. Could the families of workers have been exposed to radiation and other hazards?
  5. Housing at the mill site (5):
    Several people reported having lived in government housing on the mill site while themill was in operation. Tailings were used as fill around these houses. The residents areconcerned about harmful exposures from living so close to the mill.
  6. Contaminated soil (3):
    For many years, residents ate vegetables from gardens located where soil is now being remediated.
  7. Clean-up worker being exposed to hazardous materials :
    A resident was concerned about exposure to radiation 15 years ago when he wasremoving fire hydrants from the mill site and there were very warm Geiger counterreadings.

B. Continuing Exposure Concerns Related to the Sites

  1. Exposures resulting from the cleanup (19):
    1. Many residents feel the tailings piles and contaminated soils should be kept on themill site. They are worried about stirring things up and generating dust that mightrecontaminate previously remediated properties.
    2. People who live next to the mill site want to know what will happen to themduring the cleanup.
    3. Residents are concerned about radon gases being emitted from a permanenttailings repository.
  2. Transfer of hazardous waste from the mill site to the community (10):
    1. One resident was concerned about having taken asbestos from the mill site (alongwith other residents) and used it in fireplaces and around stoves. Asbestos fromthe mill site was disposed of in a local sanitary landfill.
    2. Materials from dismantled on-site storage buildings were used in construction offsite. Construction materials from several buildings were sent to the state prison.Could buildings built from these materials be contaminated and exposing peopleto harmful substances?
    3. Tanks were removed from the mill site and used to store grain on local farms.
    4. Radon gas migrates through the tailings into the atmosphere. Radon progeny--decay products or radium--can attach themselves to smoke or dust particles andcan damage sensitive lung tissue if inhaled over a long period of time, potentiallyresulting in lung cancer. The tailings emit gamma radiation. Gamma radiationcan also penetrate the entire body, damaging cells and potentially resulting inother types of cancer. What are the risks to the community around the Monticelloarea?
    5. It is believed that approximately 135,000 tons of tailings were used in thecommunity (e.g., as fill around utilities and basements, as a sub-base forsidewalks, driveways, and concrete slabs, and as sand mix for concrete, plaster,and mortar). Residents are concerned about exposure to radiation in and aroundtheir homes and businesses.
    6. Is the golf course in Monticello contaminated?
    7. Is the cemetery contaminated? What about exposure to workers digging gravesand doing maintenance? Are there plans to remediate the cemetery?
  3. Dangers from contaminated properties in the community (9):
    1. A residential property immediately adjacent to the mill site was previously anore-testing area. What are possible health effects?
    2. A resident expressed concern about radioactive mortar in the bricks of her son'shome; she wants to know what will be done and what, if any, dangers there are?
    3. Several people are concerned about contaminated soil in their gardens. (3)
    4. A granary where people now work was previously used as an ore-buying station;ore was weighed and dumped there. Three-fourths of this site is contaminated;there are major hot spots (at the warehouse, under the grain cleaner, and under sixsilos; a large silo has a radiation-contaminated rebar in its concrete floor).
    5. Tailings were used around houses. Are people still at risk?
  4. Contamination of groundwater/surface water (5):
    1. During the 1970s, when there was a water shortage, attempts were made to cleanand use wells on and near the mill site. Some could not be cleaned up, but somewere cleaned and put into use and are probably still being used today. Couldthese wells be contaminated?
    2. Several people expressed concern that leachate from the mill tailings is stillcontaminating surface and groundwater. Does this represent a long-term healthhazard? People are concerned about being exposed.
    3. Representatives of the Southeastern Utah District Health Department expressedconcern that present and future downstream uses of Montezuma Creek water hadnot been fully taken into consideration and proposed that the final clean-up planincorporate a suitable measure of health protection for all present and potentialfuture users.
    4. The groundwater plume extends further downstream than the location whereremediation and testing are taking place. Has this problem been studiedadequately? Will people be exposed to contaminants in the 60 years or so thatpassive restoration of groundwater is expected to take?

C. General Health Outcome Concerns

  1. Community health data/monitoring:
    Many people are concerned about the long-term health effects of living near and/orworking at the mill site. They would like to see comparisons of disease rates with ratesfor other towns and states with national data. They would also like to see long-term monitoring.
  2. Radiation health effects:
    People are concerned about the health effects of uranium, vanadium, and radon. Specifically, what are the likely health effects from drilling for ore and drilling to clean out wells at the mill site?
  3. Smoking/uranium synergism:
    What are the synergistic effects of smoking and uranium exposure leading to cancer?

D. Specific Health Outcome Concerns

  1. Cancer:
    Many people expressed concern about the numbers of people in the area with cancer andwant to know if it is related to exposure to contaminants from the mill site, either while itwas operating or after it closed. They were concerned about the following specificcancers, either because the respondent, a friend, or a family member had been diagnosedwith the cancer or because there was a concern about the number of people in thecommunity with the condition. The number enclosed in brackets indicates the number of persons expressing the concern.
    1. breast cancer [16]
    2. leukemia [13]
    3. stomach/intestinal/colon/bowel cancers (A specific concern was the high rate ofintestinal cancer in the area of town populated primarily by Spanish-speakingpeople.) [11]
    4. skin cancer (including melanoma) [10]
    5. liver cancer [6]
    6. lymphoma [6]
    7. lung cancer [5]
    8. pancreatic cancer [4]
    9. uterine/endometrial cancer [4]
    10. Hodgkin disease [3]
    11. mouth/throat cancer [2]
    12. cancer of the cervix [2]
    13. prostate cancer [2]
    14. testicular cancer [2]
    15. brain cancer
    16. multiple myeloma
    17. kidney cancer
    18. thyroid cancer
    19. mesothelioma (a person who worked at the mill and in the mines)
    20. retinoblastoma
    21. bone cancer

    There was also concern about a perception of elevated rates of cancers, particularly leukemia, in Blanding.

  2. Other illnesses:
    Residents reported a range of noncarcinogenic conditions they suspect may be caused byliving on or near the mill site, working at the mill site either when it was operating orduring the cleanup, or playing on the mill site as children. Could the following illnessesbe related to the mill site? The number enclosed in brackets indicates the number of persons expressing the concern.
    1. respiratory problems (including bronchitis, pleurisy, pneumonia, asthma, frequentcoughs, and sinusitis) [21] (A specific question: Could severe sinusitisexperienced by a number of clean-up workers be related to exposure to milltailings?)
    2. heart disease (including mitral valve prolapse and high blood pressure) [9]
    3. headaches (severe, chronic, migraine) [7]
    4. kidney disease [6]
    5. allergies [5]
    6. eye disease/vision problems [5]
    7. lumps/growths/moles [4]
    8. birth defects [4]
    9. dental problems (poor teeth, many cavities, soft teeth) [4]
    10. loss of coordination/tremors/dizziness/blackouts [3]
    11. emphysema [3]
    12. miscarriages [3]
    13. stillbirths [2]
    14. mental retardation [2]
    15. bone problems (including spinal curvature and brittle bone disease) [2]
    16. arthritis [2]
    17. digestive tract problems [2]
    18. chronic fatigue syndrome [2]
    19. pneumoconiosis (a former worker at the mill who had also worked in the mines)
    20. anemia
    21. high hematocrit
    22. nosebleeds
    23. slow healing of cuts
    24. frequent infections
    25. diabetes
    26. muscle spasms
    27. thyroid disease
    28. neurofibromatosis
    29. Parkinson disease
    30. Crohn disease

Appendix D contains information on community concerns categorized as procedural concerns and community health concerns not related to the mill site.


This section provides an historical perspective on radiation and discusses its effects on humanhealth. In the 1890s, scientists learned how to produce a type of radiation they called x-rays, andthey also found that certain naturally occurring elements emit particles and rays which theycalled radiation. Soon, radiation and radioactive materials were being used for medicalpurposes, both externally as well as internally, to diagnose and treat a host of medical conditionslike ankylosing spondylitis, acne, and cancer. Commercial use of radioactive materials evolvedand included making electron tubes, static eliminators, smoke alarms, and glow-in-the-darkwatches. Radiation has been used for many purposes since its discovery but, like a double-edgedsword, it has produced both good and bad effects as an historical review of its destructive side proves.

The effects of radiation were found to vary from one individual to the next, and with suchfactors as dose, dose rate, nonuniformity of dose distribution, type of radiation, gender, age,health status, portion of the body or organ involved, cell oxygen concentration, rate of celldivision, density of ionization, and presence of carcinogenic promoting and radiation protectivechemicals. In general, the effect increases with higher dose, higher dose rate, delivery of thedose in a shorter exposure period, larger portion of the body being exposed, the younger theindividual (especially the embryo/fetus), and the higher the internal oxygen concentrations. Toprovide statistically useful information, it was necessary to select several large groups ofindividuals that had been exposed to large doses of radiation. Some of these groups includedankylosing spondylitis patients, radium dial painters, atomic bomb survivors, cancer therapypatients, and laboratory animal studies. Another group is the uranium miners where it was foundthat the ability of radon gas to produce lung cancer was enhanced by smoking and breathingsilica dust and diesel fumes that were present inside the mines. The result is an understanding ofthe average and range of effects at high doses.

The reasons that individuals respond differently to radiation is complicated, but the reasons thatradiation can affect an individual has been intensely studied. DNA is a two-stranded, twistedmolecule inside cells that directs the formation on the proteins for human life. Radiationexposure can break one or both stands of the DNA molecule, break a bond that connects the twostrands, or alter the sequence of the DNA building blocks. These processes can kill the cell, orallow it to produce nonfunctional tumor tissue or chromosomal abnormalities. The rate of thesemutations would be higher than actually observed if it were not for repair mechanisms. A repairmechanism for broken strands cuts out the damaged section and reportedly regenerates it slowlyand faithfully.

It would be useful to know the actual effects of radiation at the relatively low doses and lowdose rates seen around Monticello. The effects at environmental levels, however, are too smallto be seen directly, or perhaps, indirectly. Scientists calculate the effect from high dose studiesand interpolate or estimate the effect at low environmental doses, or rely on epidemiologicstudies that relate health incidence rates of a potentially exposed population with a controlpopulation. The extrapolation of effects from high doses to low has been considered by many tobe linear with no threshold. This means that cutting the dose in half would reduce the effect bytwo, and there would be no dose below which there is no effect. Other possible dose-responsecharts have been suggested, but the linear-no-threshold model provides the basis for the mostradiation protection practice. An example to the contrary is cataract formation, which clearlyhas a threshold and which is regulated with that in mind. Even though a threshold may exist forcancer production in humans, the production rate is so small at low doses that it is unlikely thatthe presence or absence of a threshold can be demonstrated.

Radiation protection recommendations and regulations have grown out of the need to protectpatients, occupational workers, and the public from the potentially harmful effects of radiation,while allowing its beneficial use. Some beneficial uses include consumer products, variousindustries, and medical diagnosis and therapy. Even now, many people may just be starting tounderstand that the coal, natural gas, fertilizer, and other industries with no obvious relationshipto radioactive material actually use and distribute large quantities of radioactive material. Thedoses of radiation in medical settings can be extreme, even when compared with eitherenvironmental or bomb survivor levels. The medical community recognizes that the potentialharmful effects of radiation can be outweighed by the positive benefits of increased cancer curerates, less need for surgery, and more effective diagnoses.

Radiological effects are usually classified in two groups (nondeterministic and deterministic)based on the statistical probability or determined certainty that they are due to radiation. Thenature of how human biological quantities are changed distinguishes these. A short definition ofeach group, followed by an example, is provided below for explanation.

A. Nondeterministic Effects

A nondeterministic effect is one that occurs at random, or purely by chance, and cannot berelated 100% to any particular case. Most diseases associated with smoking are considered anondeterministic effect. For example, a person might develop lung cancer from smokingcigarettes. If the same person had not smoked, that person could have developed lung canceranyway. There is no way to determine whether a particular person's lung cancer resulted fromsmoking cigarettes; i.e., there is no proof of a cause-effect relationship. Similarly, exposure toradiation does not guarantee that an individual will develop a certain medical condition, but itdoes increase the likelihood. Cancer is a main somatic effect that may be caused by radiationexposure, and includes such types as thyroid, skin, bone, breast, liver, lung, and leukemia.

Many scientists use the "linear no-threshold" assumptions to determine nondeterministic effectsfrom radiation exposure. "No threshold" means that any exposure, no matter how small, may beharmful. "Linear" means that the probability of the development of an effect doubles as theexposure doubles.

Our present knowledge of science, radiation, and human anatomy suggests that a single changein just one of our body's cells can produce cancer or genetic defects. The body's cells aredivided into two classes: somatic cells and germ cells. The majority of cells that make up ourtissue, organs, and other parts of our body structure are somatic. The germ cells (sperm orovum) are used for reproduction. Damage to the chromosomes (a small part of the cell),whether it comes from a single radiation particle such as an alpha or beta particle, an x-ray, or agamma photon, can initiate the process. It is very important to realize that when consideringnondeterministic effects even the smallest amount of exposure to radiation may carry anassociated risk, and exposure to more radiation does produce a higher probability of a personacquiring certain medical conditions than no exposure at all.

Nondeterministic effects can be cumulative in a way that is additive, synergistic, or antagonistic. Additive effects are those where the total risk of acquiring cancer is the sum of the risks from allinsults, such as receiving two doses of radiation in a short time period. Synergistic effects arethose where the total cancer risk is greater than the sum of the individual risks, such as withsmoking and breathing radon gas. In this case, the risk from doing both is more than the riskfrom smoking plus the risk from breathing radon. Antagonistic effects are those where the totalrisk is less than the individual risks. An example would be receiving two doses of radiationseparated by a long period of time, during which the body's defense mechanisms provide partialrepair before the second exposure is received.

B. Deterministic Effects

Deterministic effects do not occur at random but have a direct cause and effect relationship. Intoxication from drinking alcohol is considered a deterministic effect. For example, a personconsuming alcohol might appear normal. After too many drinks, the person will appear a littlewoozy. If the person had not consumed alcohol he or she should not show signs of intoxication. So there appears to be proof of a cause-effect relationship between drinking and showing signsof intoxication.

Some radiation effects, including cataract formation, embryonic malformations, and radiationsickness, are deterministic. They have time and quantity thresholds, just as do the deterministiceffects for alcohol. Individuals exposed to very high radiation doses in a short period of time doshow a response. Normally, the more radiation exposure the individual experiences and thefaster the exposure occurs, the more pronounced the biological effects will be and the soonerthey will become evident. However, at low exposure rates, adverse health effects may not benoticed. At this point the radiation dose is below the threshold level. Exposures to uranium millworkers and populations surrounding mill tailings sites would have been well below the threshold level for deterministic effects.

C. Radioactive Health Effects

The amount of exposure, or dose, primarily determines whether radiation effects arenondeterministic or deterministic. Very high levels of radiation exposure, which are far aboveenvironmental levels, cause acute health effects, such as radiation sickness. Initial symptomsand the median acute dose that cause them include anorexia (97 rads), nausea (140 rads), fatigue(150 rads), vomiting (180 rads), and diarrhea (230 rads) (17, 18). The rad is the traditionalmeasurement unit for radiation absorbed dose. The larger the dose, the quicker the symptomsand signs develop. Blood syndrome occurs rapidly at 100 to 250 rads, gastrointestinal tractsyndrome at more than 1,200 rads, and central nervous system syndrome at more than 3,000rads. The clinical symptoms of blood syndrome are bleeding in various organs and decreasedblood pressure, of gastrointestinal tract syndrome are nausea and vomiting, and of centralnervous system syndrome are convulsions and disorientation. Other clinical symptoms related tohigh levels of radiation exposure are loss of hair (2,000 to 3,000 rads), skin reddening (850rads), skin damage (2,000 rads), and sterility as discussed later (18). These dose estimates canvary widely among individuals. At higher doses, the symptoms can indicate the onset of disease;for example, a highly upset stomach can indicate total destruction of cells lining thegastrointestinal tract. These types of health effects are readily noticeable--the radiation effectsare deterministic, i.e., the effect is proportional to the dose. Immediate and continuing low-levelexposures may produce later health effects. These are known as chronic or delayed health effects.

We have identified six areas of concern: cancer, mutations, infertility, degenerative effects, life shortening, and cataracts.

A large amount of data concerning cases in which humans experienced exposure to high levelsof radiation has been collected (19). For those cases, it is not the acute health effects discussedearlier that are important, but the delayed health effects. Several questions are relevant. Forinstance, if a person were exposed, did the person develop cancer, how long after exposure, wasthe source of radiation inside or outside the body, what type of cancer, and how old was theperson at the time of exposure? There is normally a latent period of about 10 to 15 years beforeany clinical signs or symptoms of carcinogenic effects appear. A lengthy plateau period, duringwhich the risk of acquiring a late or delayed health effect exists, follows latency. However,leukemia caused by high radiation doses like those at Hiroshima and Nagasaki, Japan, is anexception. Its effects have been observed much earlier than with other forms of cancer, within afew years after exposure (20, 21).

A plateau period may last about 20 to 30 years. The risk of developing cancer is constant duringthe entire plateau period. Also, the higher the risk coefficient, the greater the probability that aperson will develop cancer. The person's age at irradiation is also important. Evidence fromhuman studies shows that a person's age at time of exposure can be a major determinant ofradiation-induced cancer risk; the younger an adult is, the lower the risk of developing cancerbecomes. However, unborn babies and children have a higher risk of developing cancer relatedto radiation exposure than exposed adults have.

Although cancer is probably the most important somatic radiation hazard, three of the otherconcerns merit brief discussion: degenerative effects, life shortening, and cataracts. Degenerative effects are failures of body organs to function properly. This does not necessarilyimply complete failure, but it does indicate some amount of permanent impairment of the organ. Life shortening is believed to occur because of radiation-induced malignancies (cancer, tumors,etc.)--not because of any acceleration of the aging process. Cataracts, or vision-impairment ofthe eyes' lenses, normally occur after a long latent period. The threshold for lens opacity is 200rads, and doses of 10 rads per year over many years should not affect the vision (18).

Effects discussed to this point have involved high radiation doses and the resulting damage tocell systems, i.e., injury to several cells or groups. Radiation exposure to a single cell may alsoproduce damaging health effects. High doses of radiation to a single germ cell could lead to avariety of genetic defects in humans if the defect was passed on to the next generation. If thedose is received during pregnancy, defects could be observed in the developing fetus. Althoughthe relationship between radiation exposure and probability of mutations is unclear, someclinically observable human defects, not necessarily related to radiation exposure, are pointmutations (a single gene disorder), multiple point mutations (many gene disorders),chromosomal aberrations (e.g., Down syndrome), and spontaneous abortions.

Infertility is normally attributed to gamma-ray radiation of the human gonads. The amount ofexposure, or dose, determines the probable effect. For males, a dose of 10 rads received within ashort time period (hours to days), may cause a brief period of sterility, and 500 to 950 radscauses permanent sterility. For females, it takes 150 to 640 rads for temporary and 200 to 1,000rads for permanent sterility depending on age (18). These values are thousands of times greaterthan the doses around Monticello (22).

These effects occur at doses resulting from higher exposures or doses than existed aroundMonticello. At doses below 10 rem, delivered over many years, epidemiologic studies do notappear to show any adverse health effects. This may be the result of the body's own defense andrepair mechanisms at work, or because the effects are too small to detect. The health effectsfrom acute radiation doses are summarized in Table 1.

Table 1.

Summary of Radiation Health Effects From Acute Doses
Radiation DoseEffect
(Varies with factors like age,
gender, and physical condition)
Gray (Gy)Rads
0.1-0.5 Gy to
unborn child
10-50 radsMay cause leukemia
0.1 Gy to
the testes
10 radsBrief period of sterility
0.25-0.5 Gy25-50 radsAppearance of blood changes
1 Gy100 radsLowest dose observed to cause leukemia in Nagasaki atom bomb survivors
1-2.5 Gy100-250 radsBlood syndrome occurs starting in this range. Includes nausea and vomitingwithin hours, loss of appetite, fatigue, temporary loss of hair in 2-3 weeks,and possible death in 1-2 months
2 Gy to the
lens of eye
200 radsLens opacity threshold for total dose (not dependent on exposure time)
1.5-6.4 Gy to
the ovaries
150-640 radsTemporary female sterility
2-10 Gy to
the ovaries
200-1,000 radsPermanent female sterility
5-9.5 Gy to
the testes
500-950 radsPermanent male sterility
8.5 Gy to
the skin
850 radsSkin reddening
12 Gy or more1200 radsGastrointestinal syndrome occurs at this dose from desquamation of theintestinal epithelium. The symptoms are severe nausea, vomiting, anddiarrhea almost immediately after exposure, and death within 1-2 weeks.
20-30 Gy2,000-3,000
Permanent hair loss
30 Gy or more3,000 radsCentral nervous system syndrome occurs due to damage of the centralnervous system. Disorientation and unconsciousness occur within minutesand death within hours to several days.
NOTE: Table 1 includes the following definitions:

Gray (Gy) = International unit of measurement for radiation absorbed dose (1 Gy = 100 rads)
Rads = Traditional unit of measurement for radiation absorbed dose. One rad is defined as theabsorption of 100 ergs per gram of material.

D. Discussion

Possible adverse health effects of radiation exposure (whether internal or external) are numerousand quite complicated. Such factors as a radionuclide's toxicity, its decay scheme, the pathwayinto the human body, and the amount of dose play an important role. Cosmic rays and naturalterrestrial radioactivity from uranium, thorium, and their decay products also potentially affectone's health. Because of the city's high altitude, residents of Denver, Colorado, receive around100 milliRoentgen equivalent man (mrem) a year more than residents of such sea-level cities asMiami, Florida (18). For comparison, a typical chest x-ray can deliver a dose of 20 mrem. Using the linear-no-threshold model in ICRP 60 and NCRP 91, one would conclude that ingeographical areas with high radiation exposure rates, the health risk from radiation to thegeneral public is greater than in areas where radiation exposure rates are lower. However, thehealth risk at such doses does not correlate well with the observed effect, possibly because otherinsults to the body can be more significant (23, 24).


There are three principal ways for radioactive materials to leave a mill site during processing ofuranium or ore: airborne radioactive dust and radon-222 gas, water-soluble radionuclides, andmill tailings (both fine and coarse) (25). All of the radionuclides leaving the mill site arenaturally occurring.

A radioactive series originates with a long-lived heavy element, eventually decaying by anumber of emissions to a stable element marking the end of the series. Four series of naturallyoccurring radioactive elements exist in nature: the thorium series, neptunium series, uraniumseries, and actinium series. The uranium series (uranium-238 to lead-206) and the thoriumseries (thorium-232 to lead-208) are most likely to present biological hazards to people (26). The isotopes of both the uranium and thorium series--particularly radium-226 (radium), radon-222 (radon), thorium-234, and thorium-230 from the uranium decay series, and radium-228(mesothorium), radium-224, radon-220 (thoron), thorium-232, and thorium-228 (radiothorium)from the thorium series--are of most concern to human health. Because the radionuclides inthese series are naturally occurring, they are present throughout the environment. Theseradionuclides, along with other sources of radiation, such as cosmic radiation, all contribute toradiation levels that exist naturally. This natural radioactivity level is called the backgroundradiation level.

A. Uranium Milling in General

Uranium-bearing ores removed from the earth contain between 0.1-0.2% uranium (28). Theuranium in the Colorado Plateau ores is primarily in the form of hydrated oxide uraniumminerals. These include carnotite (K2O • 2UO3 • V2O5 • 3H2O) and tyuyamunite(CaO • 2UO2 • V2O5 • 8H2O). Mined ores are shipped to a uranium mill, where the uranium isseparated from the rock. There, the uranium is purified into yellow cake. Yellow cake is thename conventionally used for uranium ore concentrates. Depending on the separation process,carbonate or acid leaching, the yellow cake contains 85% or more of uranium oxide (U3O8), asmall percentage of red cake (vanadium pentoxide [V2O5]), and other compounds (25, 29). Theacid process, in particular, tended to release gaseous reaction products such as CO2 (carbondioxide), H2 (hydrogen), and H2S (hydrogen sulfide). The process would have also releasedunreclaimed sulfuric and hydrochloric processing acids. However, these are chemical effluents and are not radioactive.

B. Uranium and Vanadium Production Methods at Monticello

The Monticello Uranium Mill used three extraction processes: salt roast, carbonate leach, andacid leach-resin pulp. The first operation in all three processes was crushing, grinding, andscreening to produce fine sand. The salt roast process produced red cake (vanadium pentoxide[V205]) by mixing the sand with a sodium salt, roasting, washing out with water, precipitation,and heating under pressure. The other two processes took the fine sand and added liquid andchemicals to suspend the particles in the liquid. This leached or washed the uranium andvanadium out of the particles, and the useful liquid was then filtered. The carbonate leachprocess began next. Chemicals were added to the liquid, and the uranium compounds wereprecipitated. These uranium solids were filtered and steamed to make hard yellow cake(uranium oxides). Finally, in the acid leach process, chemicals were added to the remainingliquid to precipitate the vanadium compounds. These vanadium oxide solids were removed onfilters, pressed to form red cake, and heated to make black cake (29, 30).

C. Wastes Produced

The Monticello Uranium Mill, like all chemical plants, produced several wastes. The first wasresidual ore material left along the roadways and at the ore-buying station. This material camefrom trucking the ore to the station, segregating it, and moving it to the mill. Other wastesproduced at the mill site were in the form of dusts, fumes, gases, liquids, and solids.

    Dust. The second waste produced was dust from the crusher and grinder. The crushertook the ore rock and made 1-inch gravel, and then the ball mill turned the gravel intofine mesh sand. The ball mill was the dustiest operation at Monticello. The coarse dustsettled out near the grinder and was a breathing hazard to the operators. Uraniumconcentrates in the fine dust particles, which can be carried farther than coarse materialsby the wind. A large portion of the dust particles were 1 to 10 microns (0.001 - 0.01millimeters) in diameter (31). This size is respirable, meaning it can enter and lodge inthe deep, air-exchange regions of the respiratory tract. Once there, it has the potential tocause biological damage from the radiation it emits or the chemicals it contains. If theparticles are insoluble, they are partitioned so that some remain in place and producedamage by exposing the surrounding tissue to radiation; most others are coughed up andswallowed, exposing the stomach and intestines to radiation as they pass out of the body;and a small fraction may even pass directly into the bloodstream. If the particles aresoluble, some will enter the bloodstream; others are coughed up and can enter thebloodstream via the intestines.

    Fumes. The next waste was fumes released from the roaster stack at the end of theproduction cycle. For the purpose of this public health assessment, a fume is considereda process chemical that is added or formed during plant operation and released into thedischarge air. This waste stream included chlorine and hydrogen chloride gas and anestimated 1,182 kilograms (2,600 pounds) of fine particles each day. These particlescontained 0.363% uranium oxide and 1.52% vanadium pentoxide (32). Although thesize distribution of particles was not reported, they were likely small enough to be carriedfar by the wind and would penetrate deeply into the lungs of people who inhaled them. Even after such particles settle out, they can later be resuspended by the wind andvehicles and be inhaled.

    Gases. In this public health assessment, a gas is considered to be any item in the processthat is normally a gas. Radon gas is considered to be the primary gaseous waste, and itcame from all parts of the operation. This inert gas is formed during the naturalradioactive decay of uranium and thorium, and produces human exposure primarilythrough inhalation. Radon was released from essentially all parts of the millingoperation, and is still being released from the tailings piles and locations where tailingsare still present. Measurements taken in 1983 and 1984 showed that the concentrationsof radon gas on site, at the boundary, and at various locations off site exceeded theadministrative limit of 0.90 picocuries per liter (pCi/L). Remediation efforts appear to besuccessfully reducing the levels off site.

    Liquids. Liquid tailings were the leftover processing liquids. The waste resulted frommilling and leaching the ore, and from washing the filtered oxides. The main chemicalsit contained were chlorides, sulfates, carbonates, and bicarbonates of sodium and othermetals. Nitrates were added to this list late in the plant's operating history whenammonium nitrate was added as a process chemical. The liquid effluents flowed into a tailings pond and finally into Montezuma Creek, which runs through the mill site. Thewater with dissolved and suspended pollutants then became available for wateringlivestock and for irrigating crops and pasture grass.

    Solids. Solid tailings were the leftover solid process wastes. They contain the originalore and the chemicals added during extraction, less most of the uranium and vanadium. The tailings were placed into four separate piles: the Carbonate Pile, Vanadium Pile,Acid Pile, and East Tailings Pile. The damp material normally stayed in place, but as itdried, the wind blew it off the mill site, contaminating some of the nearby land. By1962, Atomic Energy Commission (AEC) representatives had covered the piles withearth and seeded them to reduce the public health risk. Rain and creek water, however,continue to wash some tailings downstream. Currently, the rate at which radon gas isbeing released from the tailings piles exceeds the EPA recommended limit of 20picocuries per square meter second (pCi/m2s). Radon gas consists of both Rn-220 andRn-222, but the short 51.6 second half-life of Rn-220 makes Rn-222 the isotope ofconcern in health evaluations. Therefore, exposures to Rn-220 would not be of healthconcern. Radon gas also is released from the piles at elevated levels, but the levels arelower than levels present when the piles were uncovered.

The radioactive materials in the gas, liquid, and solid waste streams were mainly thorium anddaughters of thorium and uranium. Radionuclides created when uranium or thorium decaystoward a stable element and emits radiation are called "daughter" products. Tables 2 and 3 showthe decay series for the uranium series and thorium series, respectively. Note that radium andradon gas are in those decay chains. Because the mill had removed most of the uranium, thetailings are less radioactive than the original ore.

Each table has 4 columns: element number, isotope, half-life, and energy. The element numberis the atomic number of the atom as listed in the Periodic Table of the Elements. Each elementmay have many radioactive isotopes--same atomic number but different mass numbers (leftsuperscript). The half-life is the time it takes for one-half of the atoms of an isotope to decay. Longer half-lives indicate a more stable radionuclide. Column 4 indicates the energy of thedecay particle. Usually the higher the particle or photon energy, the more ionizing power it has.

Radioactivity involves the spontaneous decay of an unstable atomic nucleus accompanied by theemission of a particle or photon or both. There are basically three different types of decayproducts of interest: alpha (), beta (), and gamma () rays. An alpha particle is a positivelycharged helium atom. Alpha radiation is the least penetrating of the three, subject to beingstopped by a mere sheet of paper or a few centimeters of air. It is not normally considereddangerous, except when the alpha-emitting substance has been ingested or inhaled (33). Betaparticles are electrons, either positively or negatively charged. Beta particles are easily stoppedby a thin sheet of metal or a few feet of air. Beta radiation may cause skin burns, and a betaemitter is harmful inside the body. Gamma rays are high-energy photons, somewhat higher inenergy than x-rays. Gamma radiation frequently accompanies alpha or beta emission and is themost penetrating of all three.

D. Uranium and Thorium Decay Schemes

Table 2.

Uranium Series (34)
Isotope and
Types of Emission*
Half-LifeEnergy (MeV)
(Most Prominent) *
92uranium-238 , 4.5 x 109 years4.19 ; 0.05
90thorium-234 , 24.1 days0.19 ; 0.06
91protactinium-234m **
protactinium-234 ,
1.14 minutes
6.7 hours
2.3 ; 1.0
0.48 ; 0.17
92uranium-234 , 250,000 years4.7 ; 0.05
90thorium-230 , 75,400 years4.68 ; 0.07
88radium-226 , 1,622 years4.78 ; 0.19
86radon-222 , 3.8 days5.49 ; 0.58
84polonium-218 3.1 minutes6.0 ; 0.5
82lead-214 , 26.8 minutes0.67 ; 0.35
83bismuth-214 , 19.9 minutes3.3 ; 0.61
84polonium-214 0.000164
7.68 ; 0.8
82lead-210 , 22.3 years0.02 ; 0.047
83bismuth-210 5.0 days1.16
84polonium-210 , 138.4 days5.3 ; 0.8
* = alpha particle, = beta particle, and = gamma ray
** m = The m on 234m means this is an excited or metastable state of protactinium-234

Table 3.

Thorium Series (34)
Isotope and
Types of Emission*
Half-LifeEnergy (MeV)
(Most Prominent)*
90thorium-232 , 1.4 x 1010 years4.00 ; 0.059
88radium-228 , 5.8 years0.039 ; 0.014
89actinium-228 , 6.1 hours1.2 ; 0.9
90thorium-228 , 1.9 years5.42 ; 0.08
88radium-224 , 3.6 days5.68 ; 0.24
86radon-220 , 55.6 seconds6.28 ; .055
84polonium-216 0.15 seconds6.77 ; 0.8
82lead-212 , 10.6 hours0.33 ; 0.24
83bismuth-212 , , 60 minutes6.08 ; 2.2 ; 0.7
84polonium-212 2.98 x 10-7
81thallium-208 , 3.1 minutes1.79 ; 2.6
* = alpha particle, = beta particle, and = gamma ray

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